In a rational world, New York mayor Michael Bloomberg would endorse Bruce Rauner for governor of Illinois. Both men are very rich, very smart, and believe that businessmen are best suited to run big cities.

Who ever said politics are rational? Besides, in politics image matters a lot, and to the strictly anti-gun Bloomberg—remember Bloomberg’s $2.2 million bought gun foe Robin Kelly her Illinois 2nd District congressional seat—Rauner’s romance with guns is a deal breaker.

Still, Bloomberg’s endorsement of Bill Daley mildly surprised me when it came last July. I’ve been wondering ever since what’s behind it.

Rahm Emanuel might have suggested the Daley endorsement. At least in the primary, it’s a safe guess that Rahm is hoping for a Daley win over the irritating (to Rahm) Pat Quinn. If the general election ends up being a contest between Rahm buddy Bill Daley and Rahm buddy Bruce Rauner, Rahm might have to repeat his balancing act performance of the 2008 primary battle between Barack Obama and Hillary Clinton—that is, he might have to hide under his desk until the thing is over.

Rahm and Bloomberg are friends; in fact Bloomberg has donated money to Chicago causes and Mike and Rahm have appeared together on a panel at the 2011 “Chicago Ideas Week.” It was clear to me watching them from the audience that theirs was a love affair in the making.

Rahm aside, Bloomberg and the Daley brothers, Rich and Bill, are also friends—in the sense that they go to each others’ events and say nice things about each other. According to the New York Post’s David Seifman, in June 2008, in a press conference with Bloomberg in Times Square, Daley declared, “You’re crazy if you let this guy go after only eight years.” In April 2011, a month before Daley left office, Bloomberg came to Chicago to attend an Art Institute fundraiser in Millennium Park honoring Rich and Maggie. According to a report in the Chicago Tribune, Bloomberg called Rich Daley, “the best damn mayor this country has ever seen.” When Maggie Daley died the next November, he traveled here to attend her funeral.

In 2012 Bloomberg and Bill Daley appeared together in Mike’s traveling roadshow to push immigration as a means to revitalize the American economy. (I wonder if Daley recalled Bloomberg’s suggestion the year before on “Meet the Press” that the U.S. welcome all immigrants but require that they go directly to Detroit and live there for five to ten years.)

And is it possible that the Bloomberg endorsement of Daley could turn from an asset to a liability?

The huge win for the tax-the-rich, “Tale of Two Cities,” “unapologetically progressive” Brooklyn resident Bill de Blasio in the Democratic mayoral primary on Tuesday is a humiliating defeat for Manhattan billionaire Bloomberg. De Blasio ran as the anti-Bloomberg candidate. (De Blasio’s ad maker John Cecato, David Axelrod’s partner, tweeted on election morning, “Annoy Bloomberg. Vote de Blasio today.”)

Quinn is already casting Daley as a millionaire lobbyist (he worked in the government relations department at Mayer, Brown) and banker (Midwest chairman JPMorgan Chase), who wears expensive suits and hobnobs with the 1 percent.

Consider the possibility that a general election contest ends up pitting ideologue de Blasio against unflashy manager, Republican, Bronx-born Joe Lhota—who sided with Bloomberg on supporting stop-and-frisk and on retaining Police Commissioner Ray Kelly, and supports same-sex marriage and legalizing marijuana. It wouldn’t surprise me if Bloomberg, an independent, ends up endorsing Lhota.

The son of a New York City cop, Lhota bills himself as a font of knowledge on the smallest details of municipal government, most recently chairman of the MTA, formerly Rudolph Giuliani’s budget director and then top deputy. New Yorkers like to elect Republicans as mayor; a Democrat has not been elected mayor there in 24 years.

Back to guns: Daley is going to have to temper his unconditional support for gun control, which is what made him particularly appealing to Bloomberg. Daley is running statewide and needs to quickly acquire suburban/exurban/rural pretend interests. That probably accounts for Bill’s embrace of hunters this week and his blast at Quinn for presiding over a government that allowed applications for gun-owner ID cards to get backlogged.

Bloomberg is now the lamest of ducks, his power deflating daily, even on his signature issue of gun control. As the impetus behind Mayors Against Illegal Guns, Bloomberg gave $350,000 to two Colorado state senators, both Democrats, who supported a gun control package (universal background checks and magazines limited to 15 rounds) passed in the wake of Columbine, Aurora, and Sandy Hook. They faced a recall on Tuesday and both were recalled.

If he hasn’t already, Quinn ought to put in a congratulatory call to Bill de Blasio. He may find that come primary election day in March 2014 and general election day in November 2014, de Blasio’s endorsement is the one to have.